From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Letter from Cadillac Motor Car Company discussing steering and slip angle curves.
Identifier | ExFiles\Box 170\3\ img113 | |
Date | 31th December 1936 | |
Oy file CADILLAC MOTOR CAR COMPANY DETROIT, MICHIGAN CADILLAC and LaSALLE MOTOR CARS December 31, 1936. Mr. S. Grylls, Rolls-Royce, Limited, Derby, England. Dear Grylls: Yours of December 16. I attach two charts numbered I and V showing steering angle curves for various 1936 cars and slip angle curves for Cord and Terraplane. Think this will show you the range within which we find variation of steering angle. There are various errors in reading evident in the curves, for instance all the steering curves should point to the Ackermann (theoretical) steering angle at zero lateral acceleration, and all the slip angle curves should start at zero. There are two principal reasons for these unavoidable errors. One is uncertainty as to the "upright" position of the car. There is a friction band which causes something like half a degree either side of vertical in which the car will rest. This again in the case of an independent gives two "zero" angles to the steering. The other is uncertainty as to the straight ahead running line of the car. This is quite difficult to establish. My own opinion is that it is quite unnecessary to establish either of these "zeros". I would take slip angles with the transit from an arbitrary zero and draw all slip angle curves to zero on the chart and all steering angle curves to the Ackermann. What we actually measure is the steering angle and the "attitude" of the car. We call the latter "Rear Slip Angle", assuming that the rear wheels stay parallel with the car, although we know that in some cases they don't. The front slip is equal to rear slip plus steering angle minus Ackermann, and is built up this way. | ||